Figure 5.
Ito,s is blocked by high (0.5 mM), but not by low (10 μM), concentrations of 4-AP. Outward K+ currents were recorded from a cell isolated from the septum as described in Fig. 1 during 4.5-s depolarizing voltage steps from −30 to +60 mV from a holding potential of −70 mV; all of the records displayed are from the same cell. Control currents (A) and currents in the presence of 10 μM (B) or 0.5 mM (D) 4-AP were recorded. In B and D, the currents recorded in the presence of 10 μM (B) and 0.5 mM (D) 4-AP are plotted as solid lines, and the control records (in the absence of 4-AP, A) are replotted as points to facilitate comparison. The waveforms of the 10 μM (C) and 0.5 mM (E) 4-AP–sensitive currents were obtained by off-line digital subtraction of the current records in the presence of 10 μM (B) or 0.5 mM (D) 4-AP from the controls (A). Similar results were obtained in experiments on four septum cells. Scale bars, 1 nA and 500 ms.